Download Feline Ischemic Encephalopathy

Feline Ischemic Encephalopathy
(Brain Disorder in Cats)
Basics
OVERVIEW
• ―Feline‖ refers to cat; ―ischemic‖ refers to ischemia; ―ischemia‖ is the loss of blood or blood flow to a tissue or
organ, usually due to some type of blockage of the blood vessels; ―encephalopathy‖ is a disorder of the brain
• ―Feline ischemic encephalopathy‖ is a seasonal nervous system disease that occurs in outdoor cats or cats with
access to the outdoors in North America during the summer months; usually results in sudden (acute) onset of
seizures, circling, altered mentation and/or blindness
• Abnormal migration of a Cuterebra larva in the brain of a cat that often causes a blood clot in a blood vessel
(known as ―thrombosis‖) or contraction or narrowing (known as ―vasospasm‖) of the middle cerebral artery with
resulting loss of blood flow and death of nerve tissues in part of the brain (condition known as ―ischemic
necrosis‖); also may involve loss of function (known as ―degeneration‖) of the brain as well as nerve tissue
destruction associated with the actual physical migration of the Cuterebra larva in the brain tissue
• Must be differentiated from other causes of blood vessel (known as ―vascular‖) diseases affecting the brain of
cats, as well as other nervous system diseases of the cat
SIGNALMENT/DESCRIPTION OF PET
Species
• Cats
Mean Age and Range
• Mean, 2 years of age
• Range, 1–7 years of age
SIGNS/OBSERVED CHANGES IN THE PET
• Sudden (acute) onset of nervous system signs
• Often preceded by upper respiratory signs 1–3 weeks prior to the nervous system signs (due to the migration of
the parasite [Cuterebra] in the nasal passage)
• Most common signs—seizures, circling, altered mentation, blindness
• Sometimes nervous system signs can originate from multiple locations in the nervous system; rarely see spinal
cord signs (such as weakness or paralysis)
CAUSES
• Cuterebra larvae; Cuterebra is a large fly, which lays eggs in the ground at the opening of rodent burrows; the
eggs hatch and the larvae attach to the hair and skin of a host (such as a rabbit); they enter the nose and
penetrate the moist lining, from which they migrate and eventually reach a location under the skin, where they
continue to develop; the cat may become a host as it hunts or moves in the area where the larvae are located—in
most cases, the larvae migrate to locations under the skin (especially around the head) of the cat, but if they
follow an abnormal migration pattern in the cat's body, they may end up in the brain
RISK FACTORS
• Outdoor cats; access to the outdoors
• July, August, and September in the northeast United States and southeast Canada
• Hunting cats
Treatment
HEALTH CARE
• Padded cage may be necessary if the cat is having numerous seizures
SURGERY
• Surgical removal of the parasite from the brain or spinal cord has not been reported in cats, but may be possible
if nervous system imaging techniques are available early after onset of clinical signs
Medications
Medications presented in this section are intended to provide general information about possible treatment. The
treatment for a particular condition may evolve as medical advances are made; therefore, the medications should
not be considered as all inclusive
• Supportive care and appropriate fluid supplementation, which may include thiamine (a B vitamin) and
additional potassium (administered intravenously), depending on the nutritional status of the pet
• Medications to control seizures (known as ―antiepileptic drugs‖), such as phenobarbital or diazepam to stop
cluster seizures or repeated or prolonged seizure activity (known as ―status epilepticus‖)
• A ―cocktail treatment‖ has been proposed for recently affected cats, which includes diphenhydramine
administered by intramuscular (IM) injection before giving ivermectin administered by subcutaneous (SC;
under the skin) injection and prednisolone sodium succinate administered by intravenous (IV) injection; in
addition pets receive prednisone and an antibiotic, enrofloxacin, administered by mouth (PO); ivermectin is not
approved for use against Cuterebra larvae, so your veterinarian will discuss the use of this medication with you
prior to treating your cat
• The previously described ―cocktail treatment‖ for feline ischemic encephalopathy is not necessary in a cat not
recently showing clinical signs (that is, more than a week since having clinical signs) as the parasite likely is dead
already
• Can administer dexamethasone instead of prednisone
Follow-Up Care
PATIENT MONITORING
• Sequential nervous system evaluations
PREVENTIONS AND AVOIDANCE
• Keep cats indoors
• Monthly treatment with fipronil, imidacloprid, selamectin, or ivermectin has been suggested to prevent
Cuterebra infestation
POSSIBLE COMPLICATIONS
• May continue to have uncontrolled seizures
• May continue to circle compulsively
• May have behavioral changes, such as aggression
EXPECTED COURSE AND PROGNOSIS
• After initial onset of clinical signs, many patients improve and become acceptable pets; however, persistent
nervous system deficits, seizures, circling and undesirable behavior (such as aggression) may continue
• Persistent clinical signs depend on damage caused by loss of blood flow to the brain (ischemia) and the actual
parasitic migration through the nervous tissue
Key Points
• Only occurs in outdoor cats and cats with access to the outdoors; strictly indoor cats do not develop feline
ischemic encephalopathy
• Only occurs in summer months with the majority of pets seen during July, August, and September in the
northeast United States and southeast Canada
• May not occur in major metropolitan areas that do not have the normal appropriate hosts (such as the cottontail
rabbit) for Cuterebra
Enter notes here
Blackwell's Five-Minute Veterinary Consult: Canine and Feline, Fifth Edition, Larry P. Tilley and Francis W.K. Smith, Jr. © 2011 John Wiley & Sons,
Inc.